Upgrading of a rare earth phosphate concentrate within the nitrophosphate process

摘要

In the nitrophosphate process of fertilizer production, rare earth elements (REE) can be recovered as a REE phosphate concentrate. In this process, after digestion of apatite in concentrated nitric acid, Ca(NO3)(2)center dot 4H(2)O is first separated by cooling crystallization and then the REE are precipitated in phosphate form by a partial neutralization step using ammonia. The obtained REE phosphate concentrate is contaminated by mainly calcium and iron, and the main solid phases are CaHPO4 center dot 2H(2)O, FePO4 center dot 2H(2)O and REEPO4 center dot nH(2)O.